Animal models are important experimental preparations for identifying the etiology of health problems in humans. The identification of animal models suitable for characterizing the underlying developmental biological mechanisms by which birth defects occur is especially important to the missions of the NICHD. Since malformations of the central nervous system are the most devastating developmental defects of man, the NICHD has focuse on the development of two animal models for neural tube defects. Two mouse models for neural tube defects (NTD), the TCu/tct and the curly tail were developed under contracts N01-HD-6-2925 and N01-HD-6-2926. The specific objective of this contract is to maintain and distribute the two mutant strains of mice which were developed under NICHD support. The contractor is to maintain breeding stocks of the genetically defined strains, ct/ct, TCu/TCu, tct/tct, in a healthy condition with 20 breeding paris of mutant animals available for distribution at all times. The animals are to be distributed to investigators at $21 per pair. The contractor will maintain complete breeding records on all the animals, and embryos will be frozen in order to ensure that stocks are not lost. In order to ensure that the scientific community is aware of this service, the contractor will institute a program to publicize the availability of these mutant models by advertizing them in the Jackson Laboratory catalogue, by placing advertisements in journals and by presenting data at scientific meetings.